Tuesday, January 11, 2011

Raven Wing

Thanks to Dave Hone for hosting a guest post about my recent paper over on his blog Archosaur Musings. I talked a bit about how I came to work on this specimen there, but here I’d like to talk about the specimen itself and what it means for pterosaur palaeontology.

Gwawinapterus is neat for a bunch of reasons. In Canada, we’ve got pterosaur material from Dinosaur Provincial Park that probably belongs to Quetzalcoatlus (including an amazing wing bone with embedded velociraptorine tooth!), but Gwawinapterus is the first pterosaur that is only known from Canada. It’s also, as far as I know, the first cranial material of a pterosaur from Canada (which may not be saying a lot, but there you go).

Victoria, you always pick the prettiest specimens to work on.

Gwawinapterus is also an istiodactylid pterosaur, which is interesting by its own right simply because there aren’t a lot of istiodactylids known in the fossil record, period. Howse, Milner, and Martill showed in 2001 that “Ornithodesmus” latidens from the Isle of Wight actually represented a distinct genus of pterosaur, Istiodactylus, and thus the Istiodactylidae was born. Since then, there have been some more istiodactylid teeth identified in Europe, but most other species of istiodactylids come from China. These include Istiodactylus sinensis, Nurhachius, and a host of others. All istiodactylids have been named in just the last ten years.

Prior to finding Gwawinapterus, there was no indication that istiodactylids were found in North America...with a pretty big and potentially interesting exception. Bakker (1998) noted the presence of some pterosaur teeth in the Morrison Formation that bear a striking resemblance to istiodactylid teeth. Is it possible that istiodactylid pterosaurs were present in North America since the Jurassic? Only more discoveries will help us to sort out the biogeography of the group.

And finally, all other istiodactylids are found in much older rocks from the Early Cretaceous, whereas Gwawinapterus is of Late Cretaceous age. No other pterosaurs of this age have teeth! Why do we find a toothed pterosaur so late in the game? What were the functional advantages to retaining or losing teeth in pterosaurs? Many folks in the media have asked me what kind of things Gwawinapterus was eating. It’s a fair question, although I can’t really give a very satisfactory answer – I suspect it would have been just fine at taking down small prey, and may also have been a good scavenger. The small, tightly packed teeth are somewhat reminiscent of piranha teeth, although I am leery that by saying this people will picture swarms of Gwawinapterus surrounding some big dinosaur and nibbling it to bits within minutes. Even though that would be awesome. (Incidentally, this behaviour is probably not natural for piranhas, either.)

Grr! (Thanks, Wikipedia.)

With its long snout and sharp little teeth, maybe Gwawinapterus was good at sticking its nose into carcasses and nipping bits of meat off the bones. This is not an original idea – Howse et al. proposed it back in 2001 for Istiodactyluslatidens. Whatever it was doing, Gwawinapterus was probably doing it differently from other pterosaurs at the time, and I think that’s interesting.

Literature!

Andres B, Ji Q. 2006. A new species of Istiodactylus (Pterosauria, Pterodactyloidea) from the Lower Cretaceous of Liaoning, China. Journal of Vertebrate Paleontology 26:70–78.